Open Doom3.exe with a hex editor. Find the words "GlobalMemoryStatusEx". Change the Value of only "Ex" in that line. Change the 'E' to 00 (Zero, Zero) and change the 'x' to the same. Now it runs on Windows 98SE. For those that hate XP, game on! BTW, I am running a Sony Vaio 2.8Ghz P4 with HT. 2 Gigs of ram and Windows 98SE and I can run the game on the Ultra high graphics setting with NO problem. Graphic card is nVidia GeForce 5200FX 256Mb. I dont like being forced to use any particular OS and that is what is happening with XP. So myself and like minded people figure out ways around it.